This invention relates to the field of two-way communication between a control unit and multiple terminal units, and more particularly to increased efficiency in the use of the communications channel.
There are many present day systems involving communications between a master unit of some sort and a number of satellite units, all over a single channel. Both spectrum requirements and economics require that a channel be used with maximum efficiency and there are various systems for improving efficiency. One of these is utilized in a paging system described in U.S. Pat. No. 3,855,576, and assigned to the same assignee as is the present invention. In the patented system each pager has a unique binary-coded address, consisting of two "words", and the combinations of those words and their complements are recognized by the pager and a pre-assigned character is displayed for each combination received. Each character displayed signifies a predetermined message such as "Call your office".
It would be highly advantageous if such a coding scheme could be applied to a two-way system whereby a reception by first unit of a combination of its address code words could evoke a transmission to a second unit of the appropriate combination of the address of the second unit. It would also be advantageous if at least one combination of the code of the second unit could be used to disenable normal function of the second unit and enable special functions.